Variable suspension spring rates using magnetorheological fluid

Abstract

A vehicle suspension control system includes a central suspension spring core, a first suspension spring surrounding an upper portion of the central suspension spring core, a second suspension spring surrounding a lower portion of the central suspension spring core, the first suspension spring and the second suspension spring coupled between a wheel and a fixed structure of a vehicle to inhibit movement of the wheel, a spring seat surrounding the central suspension spring core and coupled between the first and second suspension springs, the spring seat including an outer sleeve and multiple seals for retaining magnetorheological fluid between the outer sleeve and the central suspension spring core, one or more electromagnets adjacent the spring seat, and a suspension control module configured to energize the one or more electromagnets to selectively modify a viscosity of the magnetorheological fluid to inhibit movement of the first suspension spring or the second suspension spring.

What is claimed is: 
     
       1. A vehicle suspension control system comprising:
 a central suspension spring core; 
 a first suspension spring surrounding an upper portion of the central suspension spring core; 
 a second suspension spring surrounding a lower portion of the central suspension spring core, the first suspension spring and the second suspension spring coupled between a wheel and a fixed structure of a vehicle to inhibit movement of the wheel; 
 a spring seat surrounding the central suspension spring core and coupled between the first suspension spring and the second suspension spring, the spring seat including an outer sleeve and multiple seals for retaining magnetorheological fluid between the outer sleeve and the central suspension spring core; 
 one or more electromagnets adjacent the spring seat; and 
 a suspension control module configured to energize the one or more electromagnets to selectively modify a viscosity of the magnetorheological fluid to inhibit movement of at least one of the first suspension spring and the second suspension spring, 
 wherein the suspension control module is configured to selectively energize the one or more electromagnets at a specified first energization value where the viscosity of the magnetorheological fluid is sufficient to generate friction between the central suspension spring core and the outer sleeve of the spring seat to lock the outer sleeve of the spring seat in place along the central suspension spring core via friction. 
 
     
     
       2. The vehicle suspension control system of  claim 1 , wherein the suspension control module is configured to reduce energization of the one or more electromagnets to selectively allow movement of both the first suspension spring and the second suspension spring. 
     
     
       3. The vehicle suspension control system of  claim 1 , wherein the suspension control module is configured to selectively energize the one or more electromagnets to transition between:
 a first state in which the one or more electromagnets are energized at the specified first energization value to lock the spring seat to the central suspension spring core and inhibit movement of the second suspension spring; and 
 a second state in which the one or more electromagnets are energized at a specified second energization value to allow the spring seat to move relative to the central suspension spring core and allow movement of the second suspension spring, wherein the specified second energization value is less than the specified first energization value. 
 
     
     
       4. The vehicle suspension control system of  claim 3 , wherein the specified second energization value is zero. 
     
     
       5. The vehicle suspension control system of  claim 3 , wherein the suspension control module is configured to transition from the second state to the first state to facilitate the magnetorheological fluid locking the spring seat to the central suspension spring core in less than or equal to twenty milliseconds. 
     
     
       6. The vehicle suspension control system of  claim 3 , wherein,
 the suspension control module is configured to selectively energize the one or more electromagnets at a specified third energization value to partially inhibit movement of the spring seat relative to the central suspension spring core, and 
 the specified third energization value is greater than the specified second energization value and less than the specified first energization value. 
 
     
     
       7. The vehicle suspension control system of  claim 1 , wherein the one or more electromagnets include at least one coaxial magnet configured to extend in a circumference around the central suspension spring core. 
     
     
       8. The vehicle suspension control system of  claim 1 , wherein the one or more electromagnets include at least one field magnet configured to extend parallel to a longitudinal direction of the central suspension spring core. 
     
     
       9. The vehicle suspension control system of  claim 1 , wherein the suspension control module is configured to change a level of energy supplied to the one or more electromagnets over a specified period of time, according to a specified transient spring rate restriction profile. 
     
     
       10. The vehicle suspension control system of  claim 9 , wherein the specified transient spring rate restriction profile includes an increasing rate of energization during a first time period, followed by a decreasing rate of energization during a second time period subsequent to the first time period, to capture a displacement of the wheel beyond a threshold displacement value. 
     
     
       11. The vehicle suspension control system of  claim 1 , wherein the first suspension spring and the second suspension spring are coupled in series between the wheel and the fixed structure of the vehicle. 
     
     
       12. The vehicle suspension control system of  claim 1 , wherein the fixed structure includes a chassis of the vehicle. 
     
     
       13. The vehicle suspension control system of  claim 1 , further comprising at least one vehicle sensor configured to detect terrain data in front of the vehicle, wherein the suspension control module is configured to adjust a level of energization applied to the one or more electromagnets according to the terrain data detected by the at least one vehicle sensor. 
     
     
       14. The vehicle suspension control system of  claim 1 , wherein the suspension control module is configured to adjust a level of energization applied to the one or more electromagnets according to a driving stiffness setting input received via a user interface. 
     
     
       15. A method of controlling a vehicle suspension, the method comprising:
 energizing, via a suspension control module, one or more electromagnets adjacent a spring seat surrounding a central suspension spring core, the spring seat coupled between a first suspension spring and a second suspension spring each surrounding the central suspension spring core, the spring seat including an outer sleeve and multiple seals for retaining magnetorheological fluid between the outer sleeve and the central suspension spring core, wherein energizing the one or more electromagnets modifies a viscosity of the magnetorheological fluid to inhibit movement of at least one of the first suspension spring and the second suspension spring; and 
 reducing energization, by the suspension control module, of the one or more electromagnets to selectively allow movement of both the first suspension spring and the second suspension spring, 
 wherein the suspension control module is configured to selectively energize the one or more electromagnets at a specified first energization value where the viscosity of the magnetorheological fluid is sufficient to generate friction between the central suspension spring core and the outer sleeve of the spring seat to lock the outer sleeve of the spring seat in place along the central suspension spring core via friction. 
 
     
     
       16. The method of  claim 15 , further comprising:
 selectively energizing the one or more electromagnets at the specified first energization value to lock the spring seat to the central suspension spring core and inhibit movement of the second suspension spring; and 
 selectively energizing the one or more electromagnets at a specified second energization value to allow the spring seat to move relative to the central suspension spring core and allow movement of the second suspension spring, wherein the specified second energization value is less than the specified first energization value. 
 
     
     
       17. The method of  claim 16 , further comprising selectively energizing the one or more electromagnets at a specified third energization value to partially inhibit movement of the spring seat relative to the central suspension spring core, wherein the specified third energization value is greater than the specified second energization value and less than the specified first energization value. 
     
     
       18. The method of  claim 15 , wherein further comprising changing a level of energy supplied to the one or more electromagnets over a specified period of time, according to a specified transient spring rate restriction profile. 
     
     
       19. The method of  claim 18 , wherein the specified transient spring rate restriction profile includes an increasing rate of energization during a first time period, followed by a decreasing rate of energization during a second time period subsequent to the first time period, to capture a displacement of a wheel beyond a threshold displacement value.